The present invention relates to a novel glycosidation process to make intermediates useful in the preparation of indolopyrrolocarbazole derivatives which inhibit the growth of tumor cells and are therefore useful in the treatment of cancer in mammals, and the like.
In the field of cancer chemotherapy, a large number of compounds have already been put to practical use as antitumor agents. However, a need continues for the development of more efficacious compounds that work against a variety of tumors (see the Proceedings of the 47th General Meeting of the Japan Cancer Society, pp. 12-15 (1988)). This need has led to the development of indolocarbazole derivatives. (See U.S. Pat. Nos. 4,487,925; 4,552,842; 4,785,085; 5,591,842 and 5,922,860; Japanese Patent No. 20277/91; Journal of Antibiotics, Vol. 44, pp. 723-728 (1991); WO91/18003; WO 98/07433; and EP0545195 A1.) These compounds have been shown to act as topoisomerase inhibitors and therefore useful in the treatment of cancer (Cancer Chemother. Pharmacol. 34 (suppl): S41-S45 (1994)).
The success of these compounds in treating numerous cancers has necessitated the development of improved methods for their syntheses. (See Bioorg. and Med. Chem. Letters 2000, 10, 419; Tetrahedron 1997, 53, 5937; Tetrahedron 1997, 53, 585; and Synthesis 1976, 414.) The previously known methods, however, suffer from numerous problems, including the use of undesirable solvents, mercury or silver salts, low yields and formation of unwanted side-products necessitating tedious or protracted purification steps.
An object of this invention therefore is to provide a novel route to intermediates useful in the preparation of indolopyrrolocarbazole-derived antitumor substances while overcoming the problems inherent in the previously known syntheses.
The present invention is a novel glycosidation process to make intermediates useful in the preparation of indolopyrrolocarbazole derivatives which inhibit the growth of tumor cells and are therefore useful in the treatment of cancer in mammals, and the like, such as those of Formula I below. 
An embodiment of the present invention is illustrated by a process for the preparation of a compound of Formula I, 
wherein
Q is O, Nxe2x80x94R, S, or CH2;
X1 and X2 are independently selected from:
1) H,
2) halogen,
3) OH,
4) CN,
5) NC,
6) CF3,
7) (Cxe2x95x90O)NO2,
8) (Cxe2x95x90O)C1-C6 alkyl,
9) (Cxe2x95x90O)OC1-C6 alkyl,
10) OCH2OCH2CH2Si(CH3)3,
11) NO2,
12) 9-fluorenylmethylcarbonyl,
13) NR5R6,
14) OC1-C6 alkyl,
15) C1-C6 alkyl,
16) C1-C6 alkylenearyl, and
17) OC1-C6 alkylenearyl;
R and R1 are independently:
1) H,
2) (Cxe2x95x90O)C1-C6 alkyl,
3) (Cxe2x95x90O)CF3,
4) (Cxe2x95x90O)OC1-C6 alkyl,
5) 9-fluorenylmethylcarbonyl,
6) a furanose group, or
7) a pyranose group,
so long as one of R and R1 is a furanose group or a pyranose group;
R2 and R3 are independently OH or H, or
R2 and R3 are taken together to form an oxo group;
R4 is:
1) H,
2) C1-C10 alkyl,
3) CHO
4) (Cxe2x95x90O)C1-C10 alkyl,
5) (Cxe2x95x90O)OC1-C10 alkyl,
6) C0-C10 alkylenearyl, or
7) C0-C10 alkylene-NR5R6;
R5 and R6 are independently:
1) H,
2) (C1-C8 alkyl)xe2x80x94(R7)2,
3) (Cxe2x95x90O)O(C1-C8 alkyl),
4) 9-fluorenylmethylcarbonyl,
5) OCH2OCH2CH2Si(CH3)3,
6) (Cxe2x95x90O)(C1-C8 alkyl),
7) (C⊚O)CF3, or
8) (C2-C8 alkenyl)xe2x80x94(R7)2, or
R5 and R6 are taken together with the nitrogen to which they are attached to form N-phthalimido;
R7 is:
1) H,
2) OH,
3) OC1-C6 alkyl, or
4) aryl, said aryl optionally substituted with up to two groups selected from OH, O(C1-C6 alkyl), and (C1-C3 alkylene)xe2x80x94OH;
xe2x80x83which comprises the steps of:
(a) reacting a furanose or a pyranose with an activating reagent to produce an activated sugar; and
(b) coupling the activated sugar with a compound of Formula IV 
xe2x80x83wherein R1a is H if Q is O, S, CH2, or Nxe2x80x94R and R is not H, otherwise R1a is selected from R1;
xe2x80x83in the presence of an aqueous solution of alkali hydroxide and a phase transfer catalyst in a biphasic system to produce the compound of Formula I.
Another embodiment is the process described above, wherein
R and R1 are independently selected from a furanose group of Formula IIA or a pyranose group of Formula IIB, when R or R1is defined as a furanose group or a pyranose group, respectively; 
R8 is independently selected from:
1) hydrogen,
2) C1-C6 alkyl,
3) OH,
4) halogen,
5) O(C1-C6 alkyl),
6) O(C1-C6 alkylene)-aryl,
7) OSO2(C1-C6 alkyl),
8) OSO2aryl,
9) OCH2OCH2CH2Si(CH3)3,
10) O(Cxe2x95x90O)(C1-C6 alkyl),
11) O(Cxe2x95x90O)CF3,
12) azido, or
13) NR5R6, or
two R8""s on the same carbon are taken together to be oxo, xe2x95x90Nxe2x80x94R5, or xe2x95x90Nxe2x95x90R7; and
the furanose or pyranose in Step (a) is a furanose of Formula IIIA or a pyranose of Formula IIIB, respectively; 
In another embodiment, the activating reagent in Step (a) is selected from an acid halide, a sulfonate, a phosphate, a sulfate, a borate, or an acetate and the biphasic system in Step (b) is comprised of an organic solvent selected from a hydrocarbon, a nitrile, an ether, a halogenated hydrocarbon, a ketone, or an apolar aprotic solvent.
Yet another embodiment is the process described above wherein the activating reagent is selected from SOCl2 or oxalyl chloride.
A further embodiment is the process described above wherein the biphasic system is comprised of methyl-t-butyl ether, dichloromethane, or trifluorotoluene.
In still another embodiment the phase transfer catalyst in Step (b) is (Ra)4M+Axe2x88x92;
Ra is independently H or C1-C18 aliphatic hydrocarbon;
M is N or P; and
A is OH, F, Br, Cl, I, HSO4, CN, MeSO3, or PhCH2CO2.
A preferred embodiment is the process described above wherein the phase transfer catalyst is tricaprylmethyl ammonium chloride.
Another preferred embodiment is the process according to the description above, wherein the aqueous solution of alkali hydroxide in Step (b) has a concentration of about 5% to about 95% w/w and the alkali hydroxide is selected from lithium hydroxide, sodium hydroxide, potassium hydroxide, and cesium hydroxide.
Also favored is the process wherein the aqueous solution of alkali hydroxide has a concentration of about 45% to about 50% w/v and the alkali hydroxide is potassium hydroxide or sodium hydroxide.
A more preferred embodiment is a process for the preparation of a compound of Formula V, 
wherein
R4 is:
1) H,
2) C1-C10 alkyl,
3) CHO
4) (Cxe2x95x90O)C1-C10 alkyl,
5) (Cxe2x95x90O)OC1-C10 alkyl,
6) C0-C10 alkylenearyl, or
7) C0-C10 alkylene-NR5R6;
R5 and R6 are independently:
1) H,
2) (C1-C8 alkyl)xe2x80x94(R7)2,
3) (Cxe2x95x90O)O(C1-C8 alkyl),
4) 9-fluorenylmethylcarbonyl,
5) OCH2OCH2CH2Si(CH3)3,
6) (Cxe2x95x90O)(C1-C8 alkyl),
7) (Cxe2x95x90O)CF3, or
8) (C2-C8 alkenyl)xe2x80x94(R7)2, or
R5 and R6 are taken together with the nitrogen to which they are attached to form N-phthalimido;
R7 is:
1) H,
2) OH,
3) OC1-C6 alkyl, or
4) aryl, said aryl optionally substituted with up to two groups selected from OH, O(C1-C6 alkyl), and (C1-C3 alkylene)xe2x80x94OH;
R9 is:
1) H,
2) C1-C6 alkyl,
3) (C1-C6 alkylene)-aryl,
4) SO2(C1-C6 alkyl),
5) SO2aryl,
6) CH2OCH2CH2Si(CH3)3,
7) (Cxe2x95x90O)(C1-C6 alkyl), or
8) (Cxe2x95x90O)CF3;
xe2x80x83which comprises the steps of:
(a) reacting a sugar derivative of Formula VI with an acid chloride to produce the activated sugar; and 
(b) coupling the activated sugar with a compound of Formula VII 
xe2x80x83in the presence of an aqueous solution of an alkali hydroxide and tricaprylmethyl ammonium chloride in t-butyl methyl ether to produce the compound of Formula V.
And yet another preferred embodiment is a process for the preparation of a compound of Formula VIII, 
which comprises the steps of:
(a) reacting a sugar derivative of Formula IX with thionyl chloride to produce the activated sugar; 
(b) coupling the activated sugar with a compound of Formula X 
xe2x80x83in the presence of an aqueous solution of potassium hydroxide or sodium hydroxide and tricaprylmethyl ammonium chloride in t-butyl methyl ether to form the glycosidated compound XI; 
(c) deprotecting the glycosidated product XI by reacting it with catalytic palladium in he presence of hydrogen gas to form the deprotected glycosidated product XII; 
(d) reacting the deprotected glycosidated product XII with an aqueous solution of alkali hydroxide to form anhydride XIII; and 
(e) reacting anhydride XIII with 2-hydrazino-1,3-propanediol to produce the compound of Formula VIII.
Also preferred is the process as described above to make a compound of Formula V wherein Step (A) is conducted in t-butyl methyl ether or tetrahydrofuran at a temperature of about xe2x88x9210xc2x0 C. to about 30xc2x0 C. and Step (B) is conducted at a temperature of about 0xc2x0 C. to about 40xc2x0 C.
And a final embodiment is the process described above, wherein the potassium hydroxide or sodium hydroxide in step (b) is added before the tricaprylmethyl ammonium chloride.
The compounds of the present invention may have asymmetric centers, chiral axes, and chiral planes (as described in: E. L. Eliel and S. H. Wilen, Stereochemistry of Carbon Compounds, John Wiley and Sons, New York, 1994, pages 1119-1190), and occur as racemates, racemic mixtures, and as individual diastereomers, with all possible isomers and mixtures thereof, including optical isomers, being included in the present invention. In addition, the compounds disclosed herein may exist as tautomers and both tautomeric forms are intended to be encompassed by the scope of the invention, even though only one tautomeric structure is depicted.
When any variable (e.g. X1, X2, R8, R9 etc.) occurs more than one by time in any constituent, its definition on each occurrence is independent at every other occurrence. Also, combinations of substituents and variables are permissible only if such combinations result in stable compounds. Lines drawn into the ring systems from substituents indicate that the indicated bond may be attached to any of the substitutable ring carbon atoms. If the ring system is polycyclic, it is intended that the bond be attached to any of the suitable carbon atoms on the proximal ring only.
It is understood that substituents and substitution patterns on the compounds of the instant invention can be selected by one of ordinary skill in the art to provide compounds that are chemically stable and that can be readily synthesized by techniques known in the art, as well as those methods set forth below, from readily available starting materials.
As used herein, xe2x80x9calkylxe2x80x9d is intended to include both branched, straight-chain, and cyclic saturated aliphatic hydrocarbon groups having the specified number of carbon atoms. For example, C1-C6, as in xe2x80x9cC1-C6 alkylxe2x80x9d is defined to include groups having 1, 2, 3, 4, 5, or 6 carbons in a linear, branched, or cyclic arrangement. For example, xe2x80x9cC1-C6 alkylxe2x80x9d specifically includes methyl, ethyl, propyl, butyl, pentyl, hexyl, and so on, as well as cycloalkyls such as cyclopropyl, methylcyclopropyl, dimethylcyclobutyl, cyclobutyl, cyclopentyl, and cyclohexyl, and so on. The alkyl substituents may be unsubstituted or substituted with one to three substituents selected from halogen, C1-C6 alkyl, OH, OC1-C6 alkyl, O(Cxe2x95x90O)C1-C6 alkyl, O(Cxe2x95x90O)OC1-C6 alkyl, amino, amido, CO2H, CN, NO2, N3, C1-C6 perflouroalkyl, and OC1-C6 perflouroalkyl. xe2x80x9cAlkoxyxe2x80x9d represents an alkyl group of indicated number of carbon atoms attached through an oxygen bridge.
The term xe2x80x9calkenylxe2x80x9d refers to a non-aromatic hydrocarbon radical, straight, branched or cyclic, containing from 2 to 10 carbon atoms and at least one carbon to carbon double bond. Preferably one carbon to carbon double bond is present, and up to four non-aromatic carbon-carbon double bonds may be present. Thus, xe2x80x9cC2-C6 alkenylxe2x80x9d means an alkenyl radical having from 2 to 6 carbon atoms. Alkenyl groups include ethenyl, propenyl, butenyl, 2-methylbutenyl and cyclohexenyl. The straight, branched or cyclic portion of the alkenyl group may contain double bonds and may be substituted if a substituted alkenyl group is indicated.
In certain instances, substituents may be defined with a range of carbons that includes zero, such as (C0-C6)alkylene-NR5R6. If R5 and R6 are taken as H in this case, this definition would include NH2, as well as xe2x80x94CH2NH2, xe2x80x94CH2CH2NH2, CH(CH3)CH2CH(CH3)NH2, xe2x80x94CH2CH(NH2)CH3, and so on. It is intended in these cases that the substituent on the bivalent radical can be attached at any point and not limited to the terminal position.
As used herein, xe2x80x9carylxe2x80x9d is intended to mean substituted and unsubstituted phenyl or naphthyl. If substituted, it may be substituted with one to three substituents selected from halogen, C1-C6 alkyl, OH, OC1-C6 alkyl, O(Cxe2x95x90O)C1-C6 alkyl, O(Cxe2x95x90O)OC1-C6 alkyl, amino, amido, CO2H, CN, NO2, N3, C1-C6 perflouroalkyl, and OC1-C6 perflouroalkyl.
As appreciated by those of skill in the art, xe2x80x9chaloxe2x80x9d or xe2x80x9chalogenxe2x80x9d as used herein is intended to include chloro, fluoro, bromo and iodo.
When definitions such as xe2x80x9c(C1-C8 alkyl)xe2x80x94(R7)2xe2x80x9d are used, it is intended that the variable R7 be attached at any point along the alkyl moiety. Therefore, if R7 is defined as OH in this case, the definition would include the following: CH2OH, CH2CH2OH, CH(CH3)CH(OH)CH3, CH(CH3)CH(OH)CH2xe2x80x94CH(OH)CH3, and so on.
The term xe2x80x9calkylenexe2x80x9d and xe2x80x9calkenylenexe2x80x9d simply refer to an alkyl or alkenyl group as defined above, respectively, of the specified number of carbons that is divalent. For example, xe2x80x9cC1-C4 alkylenexe2x80x9d includes xe2x80x94CH2xe2x80x94, xe2x80x94CH2CH2xe2x80x94, xe2x80x94CH(CH3)CH2xe2x80x94, and so on.
The definitions of R and R1 include furanose and pyranose sugar derivatives. Preferred sugar derivatives are O-protected pyranoses, such as D-glucopyranose; 6-deoxy-6,6-difluoro-D-glucopyranose; 6-deoxy-6-azido-D-glucopyranose; 6-amino-6-deoxy-D-glucopyranose; 6-azido-D-glucopyranose; 6-amino-D-glucopyranose; 4-deoxy-4,4-difluoro-6-deoxy-6-azido-D-glucopyranose; 2-fluoro-D-glucopyranose; D-galactopyranose; 4-deoxy-D-galactopyranose; 4-deoxy-D-glucopyranose; and 4-methoxy-D-glucopyranose. (see, for examples, WO 98/07433, hereby incorporated by reference). Preferred furanoses include xylofuranose, arabinofuranose, ribofuranose, allofuranose, and 2-deoxyribofuranoses.
R9 can generally be any known O-protecting group. Examples of such protecting groups include, but are not limited to: benzyl, p-nitrobenzyl, tolyl, and the like. A more preferred protecting group is benzyl (Bn), i.e., CH2Ph. Other suitable protecting groups will be known to those of skill in the art, examples of which can be found in Protective Groups in Organic Synthesis by Peter G. M. Wuts and Theodora W. Greene; John Wiley and Sons, 3rd ed. (1999).
As used herein, xe2x80x9cbiphasic systemxe2x80x9d refers to a two-phase solvent system consisting of an aqueous phase and an organic phase.
The choice of activating reagent to activate the sugar for coupling can be readily discerned by those skilled in the art. Examples of such reagents include acid halides (such as SOCl2, POCl3, SOBr2, POBr3, PBr3 and oxalyl chloride), sulfonyl halides, and so on. The preferred reagents are thionyl chloride and oxalyl chloride. The most preferred is thionyl chloride. Other useful reagents in the activation include triphenyl phosphine/I2, and triphenyl phosphine/azidodicarboxylate.
The appropriate solvent to be used in the reaction to activate the sugar can be ascertained by the ordinary chemist. Preferred solvents are hydrocarbons (such as toluene, xylenes, heptane, and hexane), nitriles (such as acetonitrile), ethers (such as t-butyl methyl ether and tetrahydrofuran), halogenated hydrocarbons (such as methylene chloride, carbontetrachloride, chloroform, trifluorotoluene and dichlorobenzene) ketones (such as methyl isobutyl ketone and acetone), and apolar aprotic solvents (such as N,N-dimethylformamide and 1-methyl-2-pyrrolidinone). More preferred solvents are t-butyl methyl ether and tetrahydrofuran. The most preferred solvent is t-butyl methyl ether.
The activation reaction can be performed at temperatures ranging from about xe2x88x9250xc2x0 C. to about 200xc2x0 C. The preferred temperatures are about xe2x88x9210xc2x0 C. to about 30xc2x0 C.
Similarly, the appropriate solvent to use in the biphasic coupling reaction will be readily discernible to the skilled artisan. Appropriate solvents include hydrocarbons (such as toluene, xylenes, heptane, and hexane), nitriles (such as acetonitrile), ethers (such as t-butyl methyl ether and tetrahydrofuran), halogenated hydrocarbons (such as methylene chloride, carbontetrachloride, chloroform, trifluorotoluene and dichlorobenzene) ketones (such as methyl isobutyl ketone and acetone), and apolar aprotic solvents (such as N,N-dimethylformamide and 1-methyl-2-pyrrolidinone). The preferred solvents are t-butyl methyl ether, dichloromethane, and trifluorotoluene.
The coupling reaction can be performed at temperatures ranging from about xe2x88x9250xc2x0 C. to about 200xc2x0 C. The preferred temperatures are about 0xc2x0 C. to about 40xc2x0 C.
The preferred bases for the coupling reaction are alkali hydroxides, such as lithium, sodium, potassium, and cesium hydroxide. Potassium hydroxide and sodium hydroxide are more preferred. The base concentration in water can vary from about 5% w/w to about 95% w/w. The more preferred concentrations are about 45% to about 50% w/w.
The preferred phase transfer reagents in the coupling reaction are of the general formula (Ra)4M+Axe2x88x92, wherein Ra is independently H or C1-C18 aliphatic hydrocarbon; M is N or P; and A is OH, F, Br, Cl, I, HSO4, CN, MeSO3, or PhCH2CO2. A preferred phase transfer catalyst is tricaprylmethyl ammonium chloride. Other suitable phase transfer catalysts include, but are not limited to, tris-[2-(2-methoxyethoxy)ethyl]amine (TDA-1); BnEt3N+Clxe2x80x94; and (Bu)3NH+HSO4xe2x80x94.
Scheme A illustrates one possible generalized approach to the preparation of the glycosidation substrate A-6. Other approaches are known in the art, some of which are taught by Kojiri et al. in U.S. Pat. No. 5,922,860 (issued Jul. 13, 2000) and hereby incorporated by reference. Scheme B shows the phase transfer catalyzed glycosidation of A-6 to produce intermediates of type B-3. Schemes C and D show possible further modifications to afford compounds known to be useful as topoisomerase inhibitors. 